Typical Structure of Neurons

A typical neuron has an enlarged area, the cell body, which contains the nucleus. Neurons typically also have two types of specialized extensions that project away from the cell body. The branches on which information is received are known as dendrites. Each neuron usually has many dendrites. Each neuron usually also has a longer tail-like structure, or axon, which transmits information to other cells.

Axons can be branched at their tips. The axons of many kinds of neurons are surrounded by a fatty, segmented covering called the myelin sheath. This covering acts as a kind of insulation and improves the ability of axons to carry nervous system signals rapidly. In humans, axons can vary from only a fraction of an inch to more than 3 feet in length! The longest axons extend from the base of the spine all the way to the big toe of each foot.

Neurons communicate with one another through special junctions known as synapses. With the most common type of synapse, known as a chemical synapse, neurons do not actually touch. Rather, the end of the axon (or axon terminal) of one neuron is separated from the next neuron by a tiny gap called a synaptic cleft. Messages traveling from one neuron to the next must cross this gap and bind to the next neuron for the signal to continue along its path. Typically, a single neuron may be capable of receiving messages simultaneously on its dendrites and cell body from several thousand different neurons.